AP Biology. Sample Student Responses and Scoring Commentary. Inside: Free Response Question 7. Scoring Guideline. Student Samples. Scoring Commentary

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1 2018 AP Biology Sample Student Responses and Scoring Commentary Inside: Free Response Question 7 RR Scoring Guideline RR Student Samples RR Scoring Commentary College Board, Advanced Placement Program, AP, AP Central, and the acorn logo are registered trademarks of the College Board. AP Central is the official online home for the AP Program: apcentral.collegeboard.org

2 AP BIOLOGY 2018 SCORING GUIDELINES Question 7 In the tongue sole fish (Cynoglossus semilaevis), sex is determined by a combination of genetics and environmental temperature. Genetically male fish have two Z chromosomes (ZZ), and genetically female fish have one Z chromosome and one W chromosome (ZW). When fish are raised at 22, ZZ fish develop into phenotypic males and ZW fish develop into phenotypic females. However, when fish are raised at 28, the Z chromosome is modified (denoted as Z*). Z*W individuals develop as phenotypic males that are fertile and can pass on the Z* chromosome to their offspring even when the offspring are raised at 22. A cross between a ZW female and a Z*Z male is shown in the Punnett square below. Z W Z* Z* Z Z* W Z Z Z Z W (a) Predict the percent of phenotypic males among the F 1 offspring of the cross shown in the Punnett square if the offspring are raised at 22. Prediction (1 point) 75% (b) At least one Z or Z* chromosome is necessary for survival of the fish. A researcher crossed two fish and observed a 2:1 ratio of males to females among the offspring. Based on the information, identify the genotype of the male parent in the cross. Describe ONE fitness cost to the female of mating with this particular male. Identification (1 point) Z* W Description (1 point) Fewer offspring will develop/survive. 1/4 of the offspring are predicted to die. Some of her offspring will have the Z* chromosome/all of her male offspring will have a Z* chromosome.

3 7. In the tongue sole fish (Cy11ogloss11s semilaevis), sex is determined by a combination of genetics and environmental temperature. Genetically male fish have two Z chromosomes (ZZ), and genetically female fish have one Z chromosome and one W chromosome (ZW). When fish arc raised at 22 C, ZZ fish develop into phenotypic males and ZW fish develop into phcnotypic females. However, when fish are raised at 28 C, the Z chromosome is modified (denoted as Z*). Z*W individuals develop as phenotypic males that are fertile and can pass on the Z* chromosome to their offspring even when the offspring are raised at 22 C. A cross between a ZW female and a Z*Z male is shown in the Punnetl square below. z w (a) (b) Z* Z*Z Z*W z zz 1 zw w Predict the percent of phenolypic males among the F 1 offspring of the cross shown in lhe Punnctl square if the offspring arc raised at 22 C. Al least one Z or Z* chromosome is necessary for survival of the fish. A researcher crossed two fish and observed a 2: 1 ratio of males to females among the offspring. Based on the information, identify the genotype of the male parent in the cross. Describe ONE fitness cost to the female of mating with this particular male. PAGE FOR ANSWERING QUESTION 7 will SUA'\-fVl, / (\A >?-'=ii- p<.rt,m'\. h;,..f-tl"-1( r. >.H'Spffi \ hel'-l. t1.0[:lmhl,1j1..l..of wvl,- \,\)i'l. 1.J..,. 1lJ hrn <,: h1>y11 ;--tit1.. rt.t.lu.t--l,,v Y\ /.)t '-,... f- YJ>'.':u1 SIJYYIY< 1. Unauthorized copying or reuse of any part of this poge la Illegal. -26-

4 70 I 7. In the tongue sole fish (Cynoglossus semilaevis), sex is detennined by a combination of genelics and environmental temperature. Genetically male fish have two Z chromosomes (ZZ), and genetically female fish have one Z chromosome and one W chromosome (ZW). When fish are raised at 22 C, ZZ fish develop into phenotyp.ic males and ZW fish develop into phenotypic females. However, when fish are raised al 28 C, the Z chromosome is modified (denoted as Z*). Z*W individuals develop as pbenotypie mates that are fertile and can pass on the Z! chromosome to their offspring even when the offspring are raised al C. A cross between a ZW female and a Z*Z male is shown in the Punnett square bel9w. z w z zz zw (a) Predkt the percent of phenotypic males among the &s,ffspring of the cross shown in the Pun nett square if the offspring are raised at (b) At least one Z or Z* chromosome is necessary for survival of the fish. A researcher crossed two fish and observed a 2: 1 ratio of males to females among the offspring. Based on the information, identify the genotype of the male parent in the cross. Describe ONE fitness cost to the femal_ of mating with this particular male. :;_,.,. PAGE FOR ANSWERING QUESTION 7.,: ::-!.' ;.., (I (-r".j " 1 ' 'o,. n %g1n)\-::t- of- - vra it. q Unauthorized copying or reuse of any part ol lhl1 page Is Illegal. -26-

5 ADDITIONAL PAGE FOR ANSWERING QUESTION 7

6 7. In the tongue sole fish (Cynoglossus semi!aevis), sex is determined by a combination of genetics and environmental temperature. Genetically male fish have two Z chromosomes (ZZ), and genelically female fish have one Z chromosome and one W chromosome (ZW). When fish are raised at 22 C, ZZ fish develop into phenotypie males and ZW fish develop into phenotypic females. Howev.er, when fish are raised at 28 C, the Z chromosome is modified (denoted as Z*). Z*W individuals develop as phenotypic males that are fertile and can pass on the Z* chromosome to their offspring even when the offspring are raised at 22 C. A cross between a ZW female and a Z*Z male is shown in the Punnett square below. z w Z* Z* Z Z*W z zz zw (a) Predict the percent of phenotypic males among the F 1 offspring of the cross shown in the Punnett square if the offspring are raised at 22 C. (b) At least one Z or Z* chromosome is necessary for survival of the fish. A researcher crossed two fish and observed a 2: l ratio of males to females among the offspring. Based on the information, identify the genotype of the male parent in the cross. Describe ONE fitness cost to the female of mating with this particular male. PAGE FOR ANSWERING QUESTION 7 1 Li p,a w 1, \ be p b no :t y pi c. D:\ c\\ o s Unauthorized copying or rouse of any part of this paga Is Illegal. -26-

7 AP BIOLOGY 2018 SCORING COMMENTARY Question 7 Overview This question presented students with information about how environmental temperatures can impact sex determination in a species of fish. Information was provided on the ZW sex determination system in the tongue sole fish (males are ZZ, and females are ZW). If fish are raised at 28 instead of 22, the Z chromosome is modified (Z*) and Z*W individuals develop as phenotypic, fertile males. The students were shown a Punnett square of a cross between a Z*Z male and a ZW female and asked to predict the percent of phenotypic males that might result from that cross. Further information was provided that all fish must have a Z or Z* chromosome to survive, and the results of another genetic cross were given. The question asked students to use those results to identify the genotype of the male in the cross and to describe one fitness cost to the female in the cross as a result of that particular mating. The key understandings and skills students were expected to demonstrate included the following: Concepts of Mendelian and non-mendelian inheritance patters, along with the impact of abiotic factors, were used to determine outcomes of a cross and to indicate the genotypes of the individuals involved in a cross. The relationship among genotype, phenotype, and the environment was used to describe the reproductive fitness of an individual. Sample: 7A Score: 3 The response earned 1 point in part (a) for predicting that 75 percent of the F 1 offspring would be phenotypically male. The response earned 1 point in part (b) for identifying Z* W as the genotype of the male parent in the cross. The response earned 1 point in part (b) for describing that one fitness cost to the female is only 75% of their offspring will survive. Sample: 7B Score: 2 The response earned 1 point in part (b) for identifying Z* W as the genotype of the male parent in the cross. The response earned 1 point in part (b) for describing that one fitness cost to the female is a decrease in the survivability of offspring. Sample: 7C Score: 1 The response earned 1 point in part (b) for describing that one fitness cost to the female is 25% of her offspring are not expected to live.